Create architecture diagrams for loading 3D Tiles through Cesium Native

[j9liu]

This is copied from a post on our community forum soliciting feedback from our users about documentation.

While exploring the codebases for these implementations, I spent some time identifying the entry/common point(s) where cesium-native integrates with Unreal and osgEarth. The method I was looking for was updateView(). Once I understood how updateView() is called, understanding the responsibilities of cesium-native became clearer.

More explicit and publicly available architecture design of the intended 3D tile loading system, i.e going from tileset to asset accessor and how individual tiles will be streamed, as this can vastly accelerate the learning curve of any future integration / implementation.

It would be great to develop an illustrated overview of how 3D Tiles are loaded through cesium-native. This should also include references to the interfaces that users must implement to actually do something with the 3D Tiles -- e.g., IAssetAccessor, IPrepareRendererResources -- at an abstract level, and what functions would need to be called by the client, e.g., updateView

[j9liu]

As suggested by @azrogers, it could be useful to use Mermaid for these diagrams: https://mermaid.js.org/